﻿using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Reflection;
using Furion.FriendlyException;

namespace Magic.Core;

/// <summary>
/// 枚举扩展
/// </summary>
public static class EnumExtensions
{
    // 枚举显示字典缓存
    private static readonly ConcurrentDictionary<Type, Dictionary<int, string>> EnumDisplayValueDict = new();

    // 枚举值字典缓存
    private static readonly ConcurrentDictionary<Type, Dictionary<int, string>> EnumNameValueDict = new();

    // 枚举类型缓存
    private static ConcurrentDictionary<string, Type> _enumTypeDict = null;


    /// <summary>
    /// 获取枚举对象Key与名称的字典（缓存）
    /// </summary>
    /// <param name="enumType"></param>
    /// <returns></returns>
    public static Dictionary<int, string> GetEnumDictionary(Type enumType)
    {
        if (!enumType.IsEnum)
            throw Oops.Oh(ErrorCode.D1503);

        // 查询缓存
        Dictionary<int, string> enumDic = EnumNameValueDict.ContainsKey(enumType) ? EnumNameValueDict[enumType] : new Dictionary<int, string>();
        if (enumDic.Count == 0)
        {
            // 取枚举类型的Key/Value字典集合
            enumDic = GetEnumDictionaryItems(enumType);

            // 缓存
            EnumNameValueDict[enumType] = enumDic;
        }
        return enumDic;
    }

    /// <summary>
    /// 获取枚举对象Key与名称的字典
    /// </summary>
    /// <param name="enumType"></param>
    /// <returns></returns>
    private static Dictionary<int, string> GetEnumDictionaryItems(Type enumType)
    {
        // 获取类型的字段，初始化一个有限长度的字典
        FieldInfo[] enumFields = enumType.GetFields(BindingFlags.Public | BindingFlags.Static);
        Dictionary<int, string> enumDic = new(enumFields.Length);

        // 遍历字段数组获取key和name
        foreach (FieldInfo enumField in enumFields)
        {
            int intValue = (int)enumField.GetValue(enumType);
            enumDic[intValue] = enumField.Name;
        }
        return enumDic;
    }

    /// <summary>
    /// 获取枚举类型key与描述的字典（缓存）
    /// </summary>
    /// <param name="enumType"></param>
    /// <returns></returns>
    /// <exception cref="Exception"></exception>
    public static Dictionary<int, string> GetEnumDescDictionary(Type enumType)
    {
        if (!enumType.IsEnum)
            throw Oops.Oh(ErrorCode.D1503);

        // 查询缓存
        Dictionary<int, string> enumDic = EnumDisplayValueDict.ContainsKey(enumType) ? EnumDisplayValueDict[enumType] : new Dictionary<int, string>();
        if (enumDic.Count == 0)
        {
            // 取枚举类型的Key/Value字典集合
            enumDic = GetEnumDescDictionaryItems(enumType);

            // 缓存
            EnumDisplayValueDict[enumType] = enumDic;
        }
        return enumDic;
    }

    /// <summary>
    /// 获取枚举类型key与描述的字典（没有描述则获取name）
    /// </summary>
    /// <param name="enumType"></param>
    /// <returns></returns>
    /// <exception cref="Exception"></exception>
    private static Dictionary<int, string> GetEnumDescDictionaryItems(Type enumType)
    {
        // 获取类型的字段，初始化一个有限长度的字典
        FieldInfo[] enumFields = enumType.GetFields(BindingFlags.Public | BindingFlags.Static);
        Dictionary<int, string> enumDic = new(enumFields.Length);

        // 遍历字段数组获取key和name
        foreach (FieldInfo enumField in enumFields)
        {
            int intValue = (int)enumField.GetValue(enumType);
            var desc = enumField.GetDescriptionValue<DescriptionAttribute>();
            enumDic[intValue] = desc != null && !string.IsNullOrEmpty(desc.Description) ? desc.Description : enumField.Name;
        }
        return enumDic;
    }

    /// <summary>
    /// 从程序集中查找指定枚举类型
    /// </summary>
    /// <param name="assembly"></param>
    /// <param name="typeName"></param>
    /// <returns></returns>
    public static Type TryToGetEnumType(Assembly assembly, string typeName)
    {
        // 枚举缓存为空则重新加载枚举类型字典
        _enumTypeDict ??= LoadEnumTypeDict(assembly);

        // 按名称查找
        if (_enumTypeDict.ContainsKey(typeName))
        {
            return _enumTypeDict[typeName];
        }
        return null;
    }

    /// <summary>
    /// 从程序集中加载所有枚举类型
    /// </summary>
    /// <param name="assembly"></param>
    /// <returns></returns>
    private static ConcurrentDictionary<string, Type> LoadEnumTypeDict(Assembly assembly)
    {
        // 取程序集中所有类型
        Type[] typeArray = assembly.GetTypes();

        // 过滤非枚举类型，转成字典格式并返回
        Dictionary<string, Type> dict = typeArray.Where(o => o.IsEnum).ToDictionary(o => o.Name, o => o);
        ConcurrentDictionary<string, Type> enumTypeDict = new(dict);
        return enumTypeDict;
    }
}
